AC belt keeps popping off

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BlaineBug

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Wow. Thanks for this helpful insight. Like yours, mine seems to be happening under hard acceleration. What’s strange though is it was fine for 229K, AFAIK so it’s hard to imagine that the mount got tweaked.

Very cool video!
Maybe it's the crankshaft that has a little forward/back play in it now after 229,000 miles rather than the mount of the AC compressor. I forget what technical term they call that "play" in engine building land.

Edit: "End Play"
 

Dustin Jackson

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Interested to see how this plays out. After my AFM delete when I started my Tahoe for the first time my AC compressor made a loud bang when it engaged and ever since then I have noticed it is pretty loud when engaging but it never affected anything.

I don't know how long this has been happening but I always wondered if this was because I lost my mark when torqueing the harmonic balancer bolt and didn't get it slug enough on reassembly.
 
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Dave
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Interested to see how this plays out. After my AFM delete when I started my Tahoe for the first time my AC compressor made a loud bang when it engaged and ever since then I have noticed it is pretty loud when engaging but it never affected anything.

I don't know how long this has been happening but I always wondered if this was because I lost my mark when torqueing the harmonic balancer bolt and didn't get it slug enough on reassembly.
Yes, I had been having very similar symptoms for the past year or so.

If it helps, the harmonic balancer isn’t keyed on these engines and can be installed in any orientation.
 

BlaineBug

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Maybe it's the crankshaft that has a little forward/back play in it now after 229,000 miles rather than the mount of the AC compressor. I forget what technical term they call that "play" in engine building land.

Edit: "End Play"
Would it make sense that end play would be much more pronounced when racing as the motor is experiencing more torque than typical for a classy Sunday drive in the countryside?
 
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Dave
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Would it make sense that end play would be much more pronounced when racing as the motor is experiencing more torque than typical for a classy Sunday drive in the countryside?
Possibly, but I doubt it. Also, my engine isn’t the original. I believe it was replaced in either late 2013 or early 2014 with a factory new L92 based on the date stampings on the castings by the previous owner. Best guess based on CARFAX entries bracketing that time is that it has around 100K on it.
 

BlaineBug

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Possibly, but I doubt it. Also, my engine isn’t the original. I believe it was replaced in either late 2013 or early 2014 with a factory new L92 based on the date stampings on the castings by the previous owner. Best guess based on CARFAX entries bracketing that time is that it has around 100K on it.
I was under the impression that your motor had 229,000. Still too few miles for what one would expect for crank endplay but you never know how it was treated before. If it's a replacement I doubt it entirely. Could be a harmonic balancer issue though that would affect all of the pulleys. Who knows. I can't see how your shims would help now if it never had an issue before unless the pulley on the AC is to blame and has shifted.
 
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Dave
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I was under the impression that your motor had 229,000. Still too few miles for what one would expect for crank endplay but you never know how it was treated before. If it's a replacement I doubt it entirely. Could be a harmonic balancer issue though that would affect all of the pulleys. Who knows. I can't see how your shims would help now if it never had an issue before unless the pulley on the AC is to blame and has shifted.
The A/C system and body have 229K, and possibly the harmonic balancer, too. Still worth investigating as a possibility. I’ll have it in the garage next week to tear into. Thanks for all of your helpful comments on this thread - I’m grateful.
 
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Dave
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Update: I installed the stretch belt this afternoon along with the Deslugger. Checked the harmonic balancer pulley for smoothness while running and it runs true, and when I had the belts off I worked it back and forth looking for play on the rubber ring under the belt grooves and it's solid.

It was chilly here today (mid-40s) so I took it out for 3 test runs with many full-throttle pulls. The compressor engages smoothly and no problems with the belt popping off. Hopefully it's fixed. I have some road trips coming up so we will see.

1678488645564.png


 
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Dave
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Update. Stretch belt seems to be working great - no more problems with the belt slipping off so far. I let it sit for 3 days in colder temps and fired it up yesterday afternoon to take it to the grocery store. The initial compressor engagement took about half a second and was much less harsh than before adding the deslugger. After that, every time the compressor engaged it did so normally. As far as I can tell, the deslugger only engages on the first compressor engagement, and only after the ignition has been off for at least 30 minutes. That suggests a revised design than what @gooffeyguy described. I can see no downside to it at this point but I will keep an eye on it through the summer and report back.

Also, I used a sliver sharpie to mark the harmonic balancer as Don suggested and there has been no movement between the inner and outer parts.
 

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